In general, since each of a semiconductor and LCD has a high precision degree, high cleanliness and special manufacturing technique are required.
Due to such a reason, a semiconductor device is manufactured in a vacuum state to completely block contact of foreign substances contained in the air.
Accordingly, technique for sealing a vacuum operation area of a semiconductor manufacturing apparatus from the atmosphere also gives significant effects on a quality of a semiconductor product.
In the above-described processing area for manufacturing a semiconductor, an angle valve is installed to transfer fluid moved by a vacuum pump to a chamber or block the fluid.
As the angle valve includes an inlet through which the fluid is introduced and an outlet through which the fluid is discharged, and a sealing unit moves according to whether a cylinder is driven to open and close the inlet, the fluid is transferred into the chamber or blocked.
Meanwhile, as the fluid is discharged by the vacuum pump, process by-products are introduced into the angle valve. Due to this, when the bellows made of stainless steel or metal in the angle valve is exposed, particles are generated due to a chemical reaction.
The particles generated by the above-described chemical reaction are precipitated at a low temperature and stuck on the sealing unit or the like to reduce a lifespan of the angle valve. To prevent the sticking of the particles, a heater radiating heat that is greater than a predetermined temperature is attached in the angle valve to increase an inner temperature of the angle valve, thereby preventing the precipitation phenomenon of the particles.
According to the below patent document 1 of “Vacuum exhaust valve of CVD apparatus (Korean Pat. No. 10-0256768)”, in a vacuum exhaust valve of a CVD apparatus in which an operation connecting part of a valve body that is opened and closed by an actuator disposed thereabove is sealed by a bellows in a valve box having a gas inlet or a gas outlet at one side thereof and a gas outlet at a lower side thereof, a sheath heater on an elastically stretchable coil is disposed at an outer circumference side of the operation connecting part of the valve body in the bellows, a lower end thereof is fixed above the valve body, an upper end is fixed to a ceiling surface in the valve box, and then connected to a lead wire outside the valve box, a sheath thermocouple controlling a temperature of the sheath heater is concentrically disposed at an inner circumferential side of the sheath heater with the same level and the same coil winding number, and a rubber heater is attached to an outer surface of the valve box. Accordingly, the valve body and the sheath heater in the bellows may integrally operate to heat the valve body and the bellows while the valve is opened and closed, thereby preventing particles from being generated in the valve box.
However, in the patent document 1 of “Vacuum exhaust valve of CVD apparatus, as the coil shaped sheath heater and sheath thermocouple, which are connected to a piston rod, simultaneously move during a vertical movement of the actuator, the sheath heater and the sheath thermocouple may experience a reciprocal process of contraction and relaxation due to an operation of the actuator that is repeated at least hundreds of times to thousands of times per a day. As a result, the sheath heater and the sheath thermocouple may be displaced and damaged.
Also, due to a structural shape of the coil shaped sheath heater and sheath thermocouple, during relaxation, since a heat generation rate is small in comparison with a volume of the relaxed sheath heater, the heat may not be efficiently transferred into the valve box and the bellows.